std::map at() method

since C++98

// Non const version
T& at( const Key& key );

// Const version
const T& at( const Key& key ) const;

Returns a reference

to the mapped value of the element with key equivalent to key. If no such element exists, an exception of std::out_of_range is thrown.

Parameters

• key - the key of the element to find

Return value

Reference to the mapped value of the requested element.

Exceptions

Throws std::out_of_range if the container doesn't have the key specified.

Complexity

Logarithmic in the size of the container - O(log size()).

Example

Main.cpp

#include <iostream>
#include <map>

auto main() -> int {
	std::map<std::string, int> playersScores = {
		{ "player1", 50 },
		{ "super_coder", 100 },
		{ "andrew111", 41 }
	};

	std::cout << "player1 gained " << playersScores.at("player1") << " points.\n";

	// Ooops! Incorrect key!
	std::cout << "super_cader gained " << playersScores.at("super_cader") << " points.\n";
}

Possible output

player1 zdobył 50 punktów.
terminate called after throwing an instance of 'std::out_of_range'
  what():  map::at